UNITED NATIONS, Sept. 23 -- President Bush got an earful of complaints from world leaders today but responded with a mild defense of his actions in Iraq and an understated request for U.N. help.

The White House was expecting a cool response as the president appeared before the 58th annual gathering of the U.N. General Assembly. And the assembled leaders, many of whom opposed the U.S. invasion of Iraq, gave him just that. They warned that the Iraq war was a threat to the very purpose of the United Nations.

U.N. Secretary General Kofi Annan, in an unusually impassioned and sharp condemnation of U.S. policy, said "unilateralism" was an assault on the "collective action" envisioned by the late president Franklin D. Roosevelt and the other U.N. founders.

"This logic represents a fundamental challenge to the principles on which, however imperfectly, world peace and stability have rested for the last 58 years," the secretary general said. "My concern is that, if it were to be adopted, it could set precedents that resulted in a proliferation of the unilateral and lawless use of force, with or without justification."

Annan, who took the rare step of beginning his address in French rather than English, warned: "Excellencies, we have come to a fork in the road. This may be a moment no less decisive than 1945 itself, when the United Nations was founded."

French President Jacques Chirac, speaking shortly after Bush, called the war "one of the gravest trials" in U.N. history and said it "undermined the multilateral system."

In an extended critique of Bush's policy of preemptively attacking emerging threats, Chirac said: "In an open world, no one can live in isolation, no one can act alone in the name of all, and no one can accept the anarchy of a society without rules. There is no alternative to the United Nations."

Bush, who did not sit in the chamber for Annan's address, played down the contentious issue of Iraq and emphasized the good works of the United Nations. He devoted nearly half his speech to unrelated issues - weapons proliferation and sex trafficking - and made only a gentle request for assistance in Iraq. "Now the nation of Iraq needs and deserves our aid, and all nations of goodwill should step forward and provide that support," he said.

Bush spoke as if the divisions over Iraq were largely in the past. He spoke of the militants in Iraq as "against all humanity" and suggested moving beyond the disagreement over the war. "[T]here was, and there remains, unity among us on the fundamental principles and objectives of the United Nations," he said. "We are dedicated to the defense of our collective security, and to the advance of human rights. These permanent commitments call us to great work in the world, work we must do together. So let us move forward."

The president defended U.S. actions in Iraq, but he suggested those were in defense of U.N. wishes, not in violation of them. "[B]ecause a coalition of nations acted to defend the peace, and the credibility of the United Nations, Iraq is free, and today we are joined by representatives of a liberated country."

Bush played down the difficulties in Iraq, saying its people are "meeting hardships and challenges." He said the war has made the Middle East safer and the world more secure. He also hailed the actions of U.N. humanitarian services in Iraq and spoke of progress training police, rebuilding schools, hospitals, power plants and other infrastructure.

He said a new U.N. Security Council resolution would expand the U.N. role in Iraq, but he suggested that role would be in developing a constitution, training civil servants and conducting elections - not in leading the occupation. In an implicit rejection of the rapid transfer of power to Iraqis that France has proposed, Bush said "the process must unfold according to the needs of Iraqis, neither hurried, nor delayed by the wishes of other parties."

Bush was scheduled to have two days of individual meetings with leaders from France, Germany, Pakistan, India and other countries.